The present disclosure relates to technologies for outputting a required time for a rewrite operation performed by a memory unit.
A document titled “Numonyx® Axcell™ M29EW Datasheet: 256-Mbit, 512-Mbit, 1-Gbit, 2-Gbit (x8/x16, uniform block) 3 V supply flash memory” (Non-Patent Document 1) is a datasheet for a Numonyx® brand flash memory. This datasheet contains typical values and maximum values of programming and erasing time periods for data expressed in predetermined units.
In addition, Japanese Patent Publication No. H3-230398 discloses a circuit for writing data into each address, and computing an average time required for writing from the first to last addresses of a programmable read-only memory (PROM).
Characteristics of various circuits, transistors, and memory cells which operate in a memory during a data program operation vary between chips due to various factors in the fabrication process. Moreover, the actual programming and erasing time periods also vary between chips. Accordingly, the typical values and the maximum values of programming and erasing time periods contained in the aforementioned datasheet may differ from typical values and maximum values of the actual programming and erasing time periods.
However, there is sometimes a need to obtain more accurately the programming and erasing time periods which are specific to the chip. For example, when a memory performs a data rewrite operation, there is a need to allow the host CPU to know accurate programming and erasing time periods for the memory in order to confirm at an appropriate time whether the data rewrite operation has completed or not.
In view of the foregoing, it is an object of the present disclosure to obtain more accurately the programming and erasing time periods which are specific to the chip.